The present invention relates to a device that is used in association with a tractor-trailer vehicle for preventing jacknifing of these types of articulating vehicles.
"Jacknifing" is the undesired swinging of either the tractor or trailer to one side or to the other of the proper line of motion that should exist between the portions of the vehicle. It is most likely to occur when the trailer is of the semi-trailer type, having rear wheels only, and supported at the front by a lower fifth wheel plate on the tractor. This condition is more apt to occur when there are wet or icy conditions on the road wherein either the tractor or trailer tends to skid.
Devices do exist for preventing or restricting the undesired turning or swinging movement of one part of the vehicle relative to the other part. See for example U.S. Pat. Nos. 2,468,705; 3,667,778; and 3,231,295. The U.S. Pat. to Price No. 2,468,705, for example, shows in FIG. 4 a C-clamp arrangement. With this arrangement it is difficult to position the mechanism and a special fifth wheel structure is necessary which extends forwardly of the trailer. Also, with this arrangement there is a disadvantage in that the fifth wheel assembly must extend a substantial direction transversely of the vehicle to provide this clamping action at many different relative angles between the trailer and tractor. In another embodiment of the Price invention the fifth wheel assembly is provided with apertures for receiving a plunger. This arrangement is not satisfactory as it appears that the upper and lower fifth wheels must be in a particular predetermined position before the retarding force can be applied by the plunger. Furthermore, with this prior art arrangement there would appear to be an excessive amount of wear on the components that are used.
Other prior art structures are unsatisfactory for a number of other reasons. For example, some of these structures are unduly complex and all of the structures appear to require a redesign of the fifth wheel assembly.
Accordingly, one object of the present invention is to provide an improved device for preventing jacknifing of a vehicle by retarding or resisting movement between the upper and lower fifth wheel plates of the fifth wheel assembly. Another object of the present invention is to provide a device in accordance with the preceding object wherein the fifth wheel assembly is essentially unaltered in order to accommodate the device of this invention.
Still a further object of the present invention is to provide a retarding or resisting device for use with a tractor-trailer vehicle and comprising a piston having a resilient end for directly contacting the lower surface of the upper fifth wheel plate.
Another object of the present invention is to provide an adaptor plate for use with some fifth wheel assemblies for providing a bearing surface against which the piston contacts. This adaptor plate is usually necessary on some types of trucking equipment such as gravel trucks or oil tank trucks.
Still a further object of the present invention is to provide an anti-jacknifing apparatus for use in association with a fifth wheel assembly of a vehicle and which apparatus is relatively simple to install in an existing vehicle, can be manufactured relatively inexpensively, and is easy to maintain.